#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long lint;

#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))

int main()
{
	int N, K, l = 0, r = 0;
	string S; 
	cin >> N >> K >> S;
	for (int i = 0; i < K; i++)
		S[i] == '(' ? l++ : l--;
	for (int i = S.size() - 1; ; i--) {
		S[i] == ')' ? r++ : r--;
		if (l == r) {
			cout << i + 1 << endl;
			break;
		}
	}

	return 0;
}